Staining tissue specimens on a microscope slide is commonly undertaken to detect disease and abnormality, as well as for research purposes. The specimens on the microscope slide are usually thin cross sections of human tissue, and without appropriate treatment, elements of interest in the specimen are not distinguishable from other elements. In immunohistochemistry, antibodies are applied to the specimen to determine whether antigens are contained within the specimen, and also to determine the level of antigens. A stain and counterstain are usually used to indicate the areas where antibodies have bound. It is usually necessary to prepare the specimen before applying the antibodies to ensure adequate and consistent binding and staining.
In immunohistochemistry, often it is not only the detection of an antigen that is important, but also the level of antigen expression on the specimen, making consistency of binding and staining a prime concern. Similar concerns also occur with insitu hybridisation.
Preparation of the specimen and application of the antibody, and stain, if performed to a predetermined recipe, called a protocol. Each specimen undergoing a test will have a predetermined protocol for application of the antibody. There are a large number of antibodies and a number of different protocols that may be applied to each antibody, depending on the test selected, and therefore it is crucial that the correct protocol and antibody be applied to the specimen. Not only is it important to minimise errors in Immunohistochemistry, and other related processes, but it is also important to be able to detect when a mistake has been made.
The above is also true of in-situ hybridisation tests, which may be undertaken on the same instrument as immunohistochemistry, and is also used to detect disease.